Question 1

Which of the following best explains why cells are generally small in size?

Accepted Answer

Smaller cells have a higher surface area-to-volume ratio, allowing efficient exchange of materials with their environment.

Question 2

A spherical cell increases its diameter from 10 $$\mum to 20$$ $$\mum. By $$what factor does its surface area-to-volume ratio change?

Accepted Answer

It decreases by a factor of 2.

Question 3

Which of the following statements about the fluid mosaic model of the plasma membrane is correct?

Accepted Answer

Phospholipids and proteins can move laterally within the layer, contributing to membrane fluidity.

Question 4

How does cholesterol affect the fluidity of animal cell membranes at moderate temperatures?

Accepted Answer

It reduces membrane fluidity by restraining phospholipid movement.

Question 5

Which of the following molecules is most likely to diffuse directly through the lipid bilayer of a plasma membrane?

Accepted Answer

Oxygen ($$O_2)$$

Question 6

A freshwater plant cell is placed in a hypertonic solution. What will most likely happen to the cell?

Accepted Answer

It will lose water and become plasmolyzed.

Question 7

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules down their concentration gradient with the help of membrane proteins, without energy input.

Question 8

Which type of membrane protein is primarily responsible for allowing ions to pass through the membrane?

Accepted Answer

Channel proteins

Question 9

The sodium-potassium pump is an example of which type of membrane transport?

Accepted Answer

Active transport

Question 10

Which of the following best explains why polar molecules like glucose require transport proteins to cross the plasma membrane?

Accepted Answer

The hydrophobic core of the lipid bilayer prevents polar molecules from diffusing through.

Question 11

A cell is placed in an isotonic solution. What will happen to the movement of water across its plasma membrane?

Accepted Answer

Water will move in and out of the cell at equal rates.

Question 12

Which of the following is a function of membrane proteins?

Accepted Answer

All of the above

Question 13

Which process allows a cell to take in large particles, such as bacteria, by engulfing them with its plasma membrane?

Accepted Answer

Phagocytosis

Question 14

A marine fish cell is transferred to freshwater. Predict what will happen to the cell and explain why.

Accepted Answer

The cell will swell and may burst because water will enter due to osmosis.

Question 15

Which of the following best describes the role of aquaporins in the plasma membrane?

Accepted Answer

They facilitate the rapid transport of water molecules across the membrane.

Question 16

Which of the following would most likely increase the fluidity of a cell membrane at low temperatures?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in phospholipids.

Question 17

A cell uses energy to move a substance from a region of low concentration to a region of high concentration. Which equation best represents the change in free energy ($$\Delta G) $$for this process?

Accepted Answer

$$\Delta G \u003e 0$$

Question 18

Which of the following scenarios best illustrates the concept of cotransport in cell membranes?

Accepted Answer

The diffusion of sodium ions down their gradient drives the active transport of glucose into the cell.

Question 19

Which of the following is NOT a function of the plasma membrane?

Accepted Answer

Synthesizing DNA for the cell.

Question 20

Which of the following best explains why a cell placed in a hypotonic solution swells?

Accepted Answer

Water enters the cell by osmosis because the solute concentration is higher inside the cell.

Cell Membranes: Structure, Function, and Transport Mechanisms

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